Malignant brain tumors represent one of the most refractory cancers to therapy and remain incurable. Gliomas represent the most common type of brain tumors that occur in various grades, with the patient's prognosis inversely proportional to the grade. The long-term objective of my laboratory is to understand the cellular and molecular mechanisms that underlie tumor invasiveness in human gliomas. My laboratory has been active in the study of proteases and the biology of brain tumors, and data generated so far have indicated that changes in proteases are correlated with the changes in the grade of the tumors. The hypotheses is: Regulation of uPAR and uPA expression in human gliomas via a plasmid/Ad construct expressing siRNA for and uPAR and uPA message will inhibit tumor growth, invasion and angiogenesis. The Specific Aims to address these hypothesis are as follows: Specific Aim 1. Evaluate the effect of vectors expressing siRNA targeting uPAR and uPA (pU2/AdU2) on glioma cell growth, attachment, migration and invasion in vitro, la. Determine the effect of vectors expressing siRNA against uPAR and uPA single or bicistronic constructs (puPAR, puPA and pU2) on uPAR and uPA levels in glioblastoma cell lines. Ib. Compare the effect of the single or bicistronic siRNA constructs (puPAR, puPA and pU2) on glioma growth, adhesion, apoptosis and migration with that of control/mock EV (empty vector) and SV (scrambled vector) in vitro. Ic. Investigate the effect of the single or bicistronic siRNA constructs (puPAR, puPA and pU2) on the invasive behavior of human glioblastoma cells in in vitro models with that of control/mock, EV (empty vector) and SV (scrambled vector). Specific Aim 2. Determine the in vivo effects of single or bicistronic siRNA constructs for uPAR and uPA (puPAR, puPA and pU2 or Ad-uPAR/Ad-uPA/AduPAR- uPA) on invasion, angiogenesis and tumorigenicity in nude mice. 2a. Access the ability of the puPA/puPAR/pU2 constructs in pre-established intracranial tumor growth or invasiveness of human glioblastoma cell lines (SNB19 and U251) injected intracerebrally in nude mice. 2b. Determine the effect of puPA/puPAR/pU2/AdU2 constructs in preestablished intracranial tumor growth or invasiveness of two xenografts and U87 sense SPARC stable cells (U87SS) in nude mice. 2c. Evaluate the effect of single or bicistronic siRNA constructs for uPAR and uPA (puPAR, puPA and pU2/AdU2) on cerebral angiogenesis in both in vitro and in vivo models. We anticipate that these results will substantially augment our understanding of how uPAR and uPA molecules are regulated; thus, information gained should be of help in developing new therapeutic approaches to treat glioblastomas.